1. Technical Field
The present invention relates to geolocation systems in general, and in particular to a method and apparatus for rapidly determining locations of a moving radar.
2. Description of Related Art
It is tactically important for a military aircraft or other platform to be able to detect pulsed radiation from a pulsed emitter such as a radar or other radio frequency source, and to determine the position of the pulsed emitter. Generally, there are two conventional time-based methods for geolocating a pulsed emitter. The first method determines the time differences of arrival (TDOA) of emitter pulses by measuring across two antennae on either a single aircraft or two different aircraft. The second method measures the time-of-arrival (TOA) of emitter pulses as a single aircraft traverses a path. TOA measurements are collected over a number of snippets called dwells. The second method exploits the varying inter-pulse intervals due to movement of the single aircraft from one position to another.
In order for the above-mentioned methods to work, the target emitter is assumed to be stationary. If the target emitter is moving, the above-mentioned methods produce a biased estimate of the target emitter location. Such bias is significant when compared to the distance that the target emitter moves during the observation interval, and in many cases, the bias is also much larger than the effects of the measurement noise.
Consequently, it would be desirable to provide an improved method and apparatus for determining locations of a moving emitter.